Abstract

Aim: To provide the benefits of wireless SCS without an IPG and its costs or complications.

Background: For several decades spinal cord stimulation (SCS) has been in use to manage chronic pain, effectively at reduced cost
compared to conventional medical management (CMM). However, in its conventional form, the equipment is bulky, and several components
need to be implanted, most notably the implantable pulse generator (IPG). Advancements in nanotechnology and wireless devices minimized
the SCS implant significantly in size incorporating the pulse generator within the electrode thereby eliminating the IPG along with its connection
wires altogether, from implantation.

Material and Results: A review of the limited available literature on the costs of traditional SCS (TSCS) and IPG was performed and
compared to the costs of wireless SCS (WSCS). For a nonrechargeable battery the expenses during TSCS were USD 13,150 (CSD 10,591;
UK £ 7,243) in 2006 and a rechargeable battery had cost USD 20,858. TSCS maintenance costs included one battery change once in 4 years
(sometimes earlier) at a cost of USD 3,539. (IPG replacement was priced at CAD 5.071). Stimwave WSCS device (without the IPG) had a
3-year maintenance cost of 1500 Euro only. WSCS also was devoid of the complications, especially infections, due to IPG. It was equally
effective and probably with fewer complications or adverse events, especially due to the absence of the tethering effects of IPG that was
shown to contribute to electrode displacements (up to 9 cm) during normal spine movements. TSCS was reported to have 50% of infections
attributable to IPG and 10% non-infective complications caused by the IPG surgical procedures. Management of these complications was not
seen with WSCS and the expenditure could be completely avoided. In several case series, WSCS has been reported to be effective in chronic
pain secondary to failed spine surgery, herpes zoster infection and complex regional pain syndrome.Conclusions: WSCS in its miniature form with nanotechnology does not require an IPG and thus was devoid of the costs or the complications
related to IPG. TSCS equipment includes an IPG cost between 13,000 and 20,000 USD with a 4 year maintenance expenditure of 3,539 USD.
WSCS had a 3 year maintenance cost of 1500 Euro only while the outcome of pain management, so far, were encouraging. Larger clinical
data might eliminate IPG costs and complications entirely in the SCS therapy to improve the acceptability and increase the indications.

Introduction

Several advancements in the SCS equipment as well as technique ensued
over the past decade and IPG also underwent modifications to enhance its
life expectancy over a period of time. This also improved the electronics
and the dimensions of the implant. However, as an implant, IPG always
carried the associated morbidity, additional costs, complications and the
related expenditure for removal or reimplantation following infections,
failures or technical short-comings. Very limited literature exists on the
end of life (EOL) of IPG in an uncomplicated SCS case and about 48
months was an accepted figure as reported by Kumar et al, Van Buyten
and Budd [1,2,3]. In best hands, it was 49 [2] months and just 27.9 months
in 5-year-follow-up of 61 patients as reported by Van Buyten [3] with
IPG replacement in 32 patients during the time. For a nonrechargeable
battery, the EOL was at 49 months [4] with a range of 3-6 years. Apart
from EOL, complications like infection or replacement for failed therapy
were expensive adverse events to deal with.

Material and Results

Very limited literature has been published regarding the EOL of IPG
or the costs related to SCS implantation, maintenance and complications
including failures. Relevant information was obtained from published
material shown in table 1, which includes, experience from USA, Canada,
UK and Europe (Table 1). Apart from adverse events original to itself, IPG
also might contribute to additional complications and failures due to its
bulk, location, tether and tug on the rest of the equipment. Laboratory
data support such association implicating IPG in lead migration.

Bench data on IPG and electrode displacements

TSCS requires to have implanted electrode, IPG and connections
between these two. The electrode and IPG get anchored in place at their
respective surgical sites to avoid displacement during normal body
movements, especially those of spine during routine activities. The tensile/
stretch load transmitted to the electrode depends upon the IPG tethering
effect, the tissue elasticity or scarring and degree of spine motion [5].
Laboratory evidence suggests that IPG location and spine movements
exert a combined deleterious effect on the position of electrode. Up to 9
cm displacement of a thoracic SCS electrode was noted with spinal flexion/
extension movements with an IPG located in buttock. This exertion was
noted to a lesser extent when the IPG was implanted in the anterior
abdominal wall. Lead displacement of 2mm with walking, and 17mm with
trunk rotation were observed; gluteal IPG produced twice the movement
compared to an abdominal wall IPG [6]. Technical modifications like a
strain loop, anchoring materials ensued to reduce lead migrations; paddle
electrodes for the cervical SCS were promising while multichannel devices
also reduced revisions for lead migrations [7, 8].

For better performance and EOL, nonrechargeable batteries
were replaced by rechargeable batteries since battery changes and
reimplantations were part of SCS health care budget which were expected
to be fewer than 6 in a patient life span [9].

Table 1: Literature on the costs of TSCS

Author

Journal

Year

N of patients

Cost

Manca et al

Europeal J Pain

2008

52

CAD 19,486, Euro 12,653

Kumar et al

J Neurosurg spine

2006

160

CAD 23,205

Kumar & Bishop

-do---

2009

197

CAD 21,595, USD 32,882

Hornberger et al

Clin J pain

2008

NA

USD 26,005 (Nonrechargeable)
USD 35,109 (Rechargeable)

Babu et al

Neuromodulation

2013

4536
4536

USD 30,200 (Percutaneous)
USD 29,963 (Paddle electrodes)

Costs of IPG: Rechargeable and nonrechargeable

Rechargeable IPG had a higher cost (CAD 10,591 or USD 10,988) but
preferred due to its longevity (2,5), ranging between 5-9 years depending
upon the manufacturer; 9 years for Medtronic, 5 years for Boston
Scientific (claimed 10-25 years) and 6 years for Abbott (earlier St Jude).
Accordingly the maintenance costs differ between the two types of IPG;
2-3 for rechargeable compared to 5 or 6 for nonrechargeable IPG [9].

Costs of complications due the hard ware implantation

Revision of electrodes was indicated for several reasons, including
displacement, loss of stimulation. IPG might be a contributing factor as
described above [6]. An abdominal wall IPG had less incidence compared
to an IPG in gluteal region (10% and 21% respectively). The electrode
revision, although had a learning curve, was indicated in 11.3% over 10
years follow up [10]. In addition to revision surgery for displaced lead,
surgery was indicated for pain over IPG site or a rotated IPG [6,10]. In
9-11.8% patients, IPG related pain was reported [11-13] and relocation
was indicated in some of these patients; 11.8% needed IPG revision
surgeries in the experience of Quigley et al [12]. Battery failure ahead
of the EOL had 1.5% incidence in Cameron’s review of 20 year literature
on SCS [11]. IPG lasted for 50 months on average estimate of battery
life expectancy (usually within 5 years), according to Kumar et al and
Van Buyten requiring replacement in most cases [2,3] notwithstanding
the functional battery life of 25 years for a rechargeable generator from
Boston Scientific (Precision IDE clinical study) or a low figure of 10 years
[14]. In 1.2% cases, battery depletion necessitated complete explantation
of SCS [15]. Most of the times, follow up costs for SCS did not include trial
failures or these explantation costs [15,16]. Cost of minor complications
following SCS was estimated to be about USD 350. No mortality, however,
could be attributed to the morbidity associated with SCS when compared
to the age adjusted general population [17]

Infections related to IPG

Overall infection rate following SCS implantation was about 5% and
notably most infections occur in the IPG location (57%) [5]. According
to Follet et al [18] common sites for infection following SCS were IPG
pocket, the connection wire tracts and lumbar incision and 82% of these
patients had to be explanted of the device [5]. Other adverse events
related to IPG include pocket pain in up to 11.8% cases [5,11] indicating
revision surgery in some patients. Burning pain due to electric leakage
was reported in some.

Discussion

Today health care budget requires medical audits on treatment
expenditure and clinical outcomes in a meaningful way to improve
safety and efficacy. Therapeutic efficacy of SCS in chronic intractable
pain has been established in several reports and refining the technology
improved the patient comfort and treatment results. However, there exists
scope for improvement in SCS outcomes exists to reduce complications
or their associated costs. A large percentage of patients, as high as 50%
reportedly have failed the trial period utilizing conventional SCS devices
[11-13], while additional failures came from equipment complications
contributed by the migration/fracture of the electrodes as well as IPG
failures and complications in re-charging or re-implantation. Postsurgical
complications like infection, hemorrhage and painful operative
wounds were frequently seen associated with IPG and its extension wires.
Additionally, SCS in its conventional form is incapable of reaching some
anatomical locations to provide targeted therapeutic localized pain relief
[11-13].The TSCS therapy, its complications and IPG related costs have
been a matter of concern (Table 2 and 3) especially in the light of recent
nanotechnology advances and wireless approaches to SCS, the most
charming factor being the implantation of a single nanoelectrode device
with capabilities of wireless access to a remove antenna.

This wireless neuromodulation requires implantation of an electrode
embedded with in-built receiver to contact an external wireless pulse
generator (EPG or WPG) without any requirement for additional
implants in the form of an IPG or its connection cables. Thus, WSCS
is truly minimally invasive requiring minimal anesthesia and minimal
hospital hours of stay to minimize health care expenses. In addition,
the implant, in case of revision or failures requires simple procedures
or explantation since the IPG and connecting wires were not implanted.
The tethering effects due to the battery and its extensions are eliminated
effectively [19] as the electrode communicates with the antenna that is
located externally (Figure 1,2). This wireless device is fully programmable
with a wide frequency range between zero and 10,000 Hz. Its effective
neuromodulation therapy has been so far reported in several case series
and illustrative cases demonstrating the safety as well as feasibility in
the management of chronic intractable pain due to failed spinal surgery,
herpes zoster and others [20-22]. Wireless neuromodulation exhibited
outcomes comparable to TSCS in many cases and could be employed for
SCS, peripheral nerve stimulation and dorsal root ganglion stimulation.
Further experience in multiple disease conditions with larger patient
groups might support this novel therapeutic approach to eliminate IPG
form SCS and improve the acceptability by both the patients and thirdparty
audit.

Figure 1: MRI compatible electrode with nanostimulator and micro circuit
to contact wireless pulse generator. This is the only implantable component
required for WSCS